System architecture for varying rate transmission

ABSTRACT

A system receives an incoming datastream at an incoming data rate or transmits an outgoing datastream at an outgoing data rate. The system may include a detection circuit to monitor the signal quality of the datastream. Responsive to changes in the monitored signal quality, the system may switch the data rate from a first data rate to a new data rate. If signal conditions are favorable, the system may switch to a higher data rate than the first data rate. If signal quality conditions worsen, the system may switch from the first data rate to a lower data rate to allow for a reduction in error rate.

PRIORITY CLAIM

This application claims priority to provisional application Ser. No.62/074,271, filed 3 Nov. 2014 and to provisional application Ser. No.62/245,558, filed 23 Oct. 2015, each of which being entirelyincorporated by reference.

TECHNICAL FIELD

This disclosure relates to varying connection rates for wirelineconnections.

BACKGROUND

High speed data networks form part of the backbone of what has becomeindispensable worldwide data connectivity. Within the data networks,network devices, such as synchronization devices, maintain networkconnection integrity among interconnected devices. Improvements inconnection quality management will further enhance performance of datanetworks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example device that may include connection qualitymanagement circuitry.

FIG. 2 shows example rate adjustment circuitry.

FIG. 3 shows example data rate adjustment logic, which may beimplemented on the adjustment circuitry.

FIG. 4 shows communication link establishment logic.

DETAILED DESCRIPTION

The disclosure below concerns techniques and architectures forimplementing data rate adjustment in wireline networks, e.g., twistedpair networks, coaxial networks, optical networks, or other guidedmedia. In some cases, networks may experience transient changes insignal quality resulting from varying signaling conditions. Signallevels, signal-to-noise ratio (SNR), bit error rates, symbol errorrates, and/or other signal quality levels may change along with thevarying signaling conditions. The architectures and techniques discussedbelow allow the system to adjust the data rate used in communication toincrease and/or decrease the ratio of robustness to signal quality lossas the signal conditions change. For example, the system may reduce itsdata rate if poor signaling conditions are experienced. If the source ofthe poor signaling conditions is transient or if favorable signalingconditions are later present, the system may increase its data rate.

The example device described below provides an example context forexplaining the techniques and architectures for varying data ratetransmission. FIG. 1 shows an example device 100. The device 100 may bea communication device, such as a rack mount server. However, the device100 may be virtually any device implementing data transmission. Forexample, a cable or satellite set-top box, a console gaming system,router, network switch, or a laptop, tablet, or personal desktopcomputer may use the techniques and architectures described below. Thecommunication device may include a user interface 116 to allow foroperation of the device.

The device 100 may include network interface circuitry 101, which mayinclude transceiver 102 to support RF and/or optical communication inwireline media, e.g. wired or other wave-guided media, or free-spacemedia. For example, the techniques and architectures may be applied toEthernet, serial, parallel, optical, proprietary communication systems,and/or other network systems communicating over wireline media such ascoaxial cable, twisted pairs, optical fibers, or other guided media. Thetransceiver 102 may support communications at multiple data rates. Forexample, the transceiver 102 may establish communication links tocommunication networks at one or more supported data rates. The device100 may further include one or more processors 104 to support executionof applications and operating systems, and to govern operation of thedevice 100. The device 100 may include memory 106 for execution supportand storage of system instructions 108 and operational parameters 112.Signal processing circuitry 114 (e.g., an Analog to Digital Converter(ADC), baseband processors or other signal processing circuits) may alsobe included to support transmission and reception of networking signals.The signal processing circuitry 114 may further include adjustmentcircuitry 108, as described below.

In some networking applications, the device 100 may implement a networkprotocol that supports transmission over a physical media dependent(PMD) network portion. In some cases, PMD network segments may beassociated with varying error rates. For example, error rates may bedependent on cable design, cable length, temperature, physicalpositioning, cable defects, interference, noise shielding, and/or otherphysical effects on the transmission media.

In an example scenario, a category 6A (CAT 6A) cable below 100 m inlength may have robust support for 10G Ethernet signaling using variousprotocols. However, lengths above 100 m may be supported in certainenvironments and not necessarily supported in other environments. Insome cases, the error rate may be suitable for a first data rate whenother more favorable signaling conditions are also present. Examples ofsignaling conditions that the protocol may analyze include transmissionmedia temperature, radiative interference, temperature of signalgeneration circuitry, and/or other time-varying conditions. However, asthe conditions deteriorate, the error-rate may pass into undesirablelevels, for example, a level at or above an error threshold. The systemmay respond by adjusting the data rate to a level with desirableperformance (e.g., error rate under a predetermined threshold). Forexample, a system operating at 10G on a CAT 6A cable above 100 m inlength may switch to 5G or 2.5G operation, or other data rates, inresponse to a detected reduction in SNR. The system may return to 10Goperation if the reduction in SNR subsides. Similarly, a systemoperating at 5G on a CAT 5e cable, which may lack support for a 200 Mhztransmission bandwidth, may switch to 2.5G or 1G operation, or otherdata rates, in response to a reduction in SNR relative to initialsignaling conditions.

Some devices connect to dense sets of cables. For example, the outercasings (e.g., the insulation layers) of various cables packed togethermay be in physical contact with one another. Signals traveling along thecables may cause radiated and/or evanescent fields. These fields maylead to cross-talk among the cables. Cross-talk may lead to time-varyingchanges in transmission performance across individual cables. Forexample, interference levels may increase in a first cable whenneighboring cables are actively carrying signals. However, when networkactivity on the neighboring cables ceases or decreases, the interferencelevels may decrease. Therefore, the first cable may support a firstbit-rate at times of lower activity in neighboring cables and a secondbit-rate at times of higher activity in neighboring cables, where thefirst bit-rate is greater than the second bit-rate.

Wireline networking may have connectivity up-times that are longer thanthose of wireless networks. For example, a wired Ethernet connection mayremain connected for periods of a day, whereas a wireless connection mayfall into an inactive state when the activity levels of the connecteddevice fall below a certain level, e.g., entering a suspend or sleepmode. In addition, if the data rate of a wired connection is throttleddown, e.g., responsive to connectivity failures, the data rate may notbe ratcheted up again until the connection is brought down andsubsequently renewed. This throttle down bias may occur even where theconnectivity failures inciting the data rate throttle down are cause bytemporary signaling condition degradations that recover shortlyafterward. Over the course of an up-time, a wireline communication linkmay be throttled down multiple times without corresponding data rateincreases when signal conditions recover. Data rate adjustment systemsmay address this throttle down bias by allowing for communication linkdata rate increases responsive to favorable signaling conditionsalongside communication link throttling responsive to unfavorablesignaling conditions.

FIG. 2 shows example adjustment circuitry 200. The adjustment circuitry200 may include detection circuitry 202 within network interfacecircuitry 101. The detection circuitry 202 may determine a signalingcondition on the data line 210, which provides connectivity between thenetwork interface circuitry and the wireline network 299.

For example, the detection circuitry 202 may determine a signalcharacteristic, such as an SNR, a bit-error rate, a symbol error rate,or other signal characteristic. Additionally or alternatively, thedetection circuitry 202 may determine ambient conditions that may affectsignal quality such as radiated emission levels, electromagneticinterference (EMI), e.g., from physical systems such as neighboringsignal lines, nearby processing systems or other electronic equipment,or other EMI sources, temperature, and/or other ambient conditions.

The detection circuitry 202 may include analog frontend circuitry 232,analog-to-digital converters 234, error measurement and correctioncircuitry 236, environmental sensors 238, and/or other circuitry tosupport detection of the signal level and/or signal conditions. Thedetection circuitry 202 may be integrated with and/or implemented onother signal reception and transmission circuitry used to support datareception or transmission, such as network interface circuitry 101. Thedetection circuitry 202 may provide the detected signal level and/orsignaling condition indicators to adjustment processing circuitry 204 onthe signal condition output. This signal condition output may include aninternal bus or network connection.

The analog frontend (AFE) circuitry 232 may include analog signalreception/transmission circuitry such as power amplifiers,modulators/demodulators, low noise amplifiers, optical amplifiers,optical modulators, photodiodes, or other circuitry to supportreception/transmission of analog signals over the wireline medium.

The analog-to-digital converter (ADC) circuitry 234 may convert thereceived physical analog signals into digital line coded signals. TheADC circuitry 234 may be paired with digital-to-analog converter (DAG)circuitry to support conversion of line-coded digital signals to analogwaveforms for transmission. The ADC circuitry may include power sensorswhich may be used by the detection circuitry 202 to make signal leveland noise floor power measurements to determine an SNR.

The error measurement and correction (EMC) circuitry 236 may analyzereceived error correction frames, such as parity coding frames, forwarderror correction blocks, redundancy checks, concatenated coding, turbocoding frames, repeat request signals, or other error correction frames.The EMC circuitry 236 may analyze the error correction frames todetermine signaling conditions, such as error rates or SNR. For example,the EMC circuitry 236 may self-compare or compare error correctionframes against received data frames to determine instances of errorwithin the signal. The EMC circuitry 236 may count the instances todetermine error rate or infer a SNR based on the frequency of theinstances.

The environmental sensors 238 may include temperature, vibration,voltage, current, signal power level, photodiodes, RF antennas, or otherenvironmental sensors. The detection circuitry 202 may pull data fromthe environmental sensors 238 to determine environmental conditions thatmay affect signaling conditions.

The adjustment processing circuitry 204 may respond to the detectedlevels and conditions by causing the system to switch data rates. Forinstance, by sending a message to a communication controller, by settinga rate parameter, flag, or value in memory, or otherwise signaling orcausing a switch in data rate.

The adjustment processing circuitry 204 may also receive externalindicators 240, e.g., from application layers, operators, operatingsystems, or other sources that may specify specific data rate targets.The external indicators may be received at command input 250.Additionally or alternatively, the external indicators may be receivedby the adjustment processing circuitry 204 from the network 299, e.g.,from infrastructure nodes, via the detection circuitry 202 and signalcondition output 206.

FIG. 3 shows example data rate adjustment logic 300, which may beimplemented in the adjustment circuitry 200. The detection circuitry 202may receive incoming signals on a data line 210 at a first data rate(302). The detection circuitry 202 may monitor the incoming signals(303). The detection circuitry 202 may detect signaling conditions forincoming signals (304). For example, the EMC circuitry 236 may determinea symbol error rate, or the ADC circuitry 234 may determine the SNR. Thedetection circuitry 202 may send an indicator of the detected signallevel and/or detected condition to the adjustment processing circuitry204 (306). The adjustment processing circuitry 204 receive the indicator(308). Based on the received indicator, the adjustment processingcircuitry 204 may determine if one or more criteria are met for changingthe data rate being used on the data line 210 (310).

For example, the adjustment processing circuitry 204 may compare thesignal level and/or signaling conditions to threshold values todetermine if the criteria are met. When the signal level and/orconditions exceed a threshold the adjustment processing circuitry 204may determine to increase the data rate. When the signal level and/orconditions fall below a threshold, the adjustment processing circuitry204 may determine to decrease the data rate. Thresholds for increasingand decreasing the data rate may be staggered to avoid repeated datarate switching near a two-way transition. However, the adjustmentprocessing circuitry 204 may use other techniques to avoid rapid datarate changes in systems using overlapping thresholds for data rateincreases and decreases.

Additionally or alternatively, the criteria may include timer back-offperiods for data rate switching. For example, once the data rate isdecreased, the adjustment processing circuitry may wait for a back-offtimer to expire before allowing a data rate increase, e.g., theadjustment processing circuitry 204 may forgo data rate adjustmentsduring the back-off period. A timer back-off period may also assist theadjustment processing circuitry 204 in avoiding repeated data ratechanges where transient conditions may be reducing signal quality forshort periods and then returning to a steady state or increasing signalquality for short periods and then returning to a steady state.

If the criteria are met, the adjustment processing circuitry 204 mayswitch the data rate of the system (312). For example, the adjustmentprocessing circuitry 204 may cause an interruption of the data stream toinitiate auto re-negotiation at a second data rate by sending a commandto the detection circuitry 202. If the criteria are not met, theadjustment processing circuitry 204 may allow the system to continueoperation at the first data rate (314). The detection circuitry 202 maycontinue to monitor incoming signals on the data line 210 (303).

The detection circuitry 202 may monitor signal conditions for theincoming signals by monitoring indicators within the incoming signals.For example, signal conditions may be indicated by data frames receivedfrom other network devices detailing detected conditions at thosedevices. Additionally or alternatively, signal condition indicators mayinclude errors, corrupted bits/symbols, noise levels, parity coding dataframes or other error correction frames, or other signal or dataparameters present on incoming signals that may be used to detect failedtransmission attempts. Parity coding frames may be blocks of parity bitssent to the system by other network devices. The EMC circuitry 236within the detection circuitry 202 may compare the parity coding framemay be to other frames or self-compare the parity coding frame todetermine estimates of bit-error rates symbol-error rates or otherindications of failed transmission attempts. In some implementations,the parity coding frames may be received periodically or aperiodicallyby the detection circuitry 202. For example, parity coding frames may bereceived by the detection circuitry 202 at regular intervals, e.g.,microsecond, millisecond, or other intervals. Additionally oralternatively, network interface circuitry 101 may add or remove paritycoding frames from a data stream responsive to commands from networkinfrastructure nodes or client devices.

The adjustment processing circuitry 204 may receive an externalindicator 240, e.g., from a system operator, of a selected data rate(318). The adjustment processing circuitry 204 may determine if theselected data rate is supported by current conditions (320). If theselected data rate is supported, the adjustment processing circuitry 204may switch the system to the selected data rate (322). If the data rateis not supported, the adjustment processing circuitry 204 may return anerror message for the system operator (324). In various implementations,the adjustment processing circuitry 204 may proceed to switch to theselected data rate or wait for further confirmation before switching.

Moving now to FIG. 4, communication link establishment logic 400 isshown. The network interface circuitry 101 may receive a command, e.g.,from an application layer, operating system, adjustment processingcircuitry, or other control circuitry, to establish a communication linkto a wireline network (402). Additionally or alternatively, the networkinterface circuitry 101 may initially establish the communication linkto the wireline network when network connectivity is detected over thewireline medium that connects the network interface circuitry 101 to thewireline network (404). The network interface circuitry 101 maydetermine, e.g., responsive to the command or stored instructions, theestablishment protocol to be implemented during communication linkestablishment (406). For example, the network interface circuitry 101may select among auto-negotiation protocols and retrain protocols, e.g.,fast retrain or other retrain protocols.

If auto-negotiation is selected, the network interface circuitry 101 mayestablish a negotiation link using initial parameters with broadcompatibility, e.g., default connection parameters (408). The networkinterface circuitry 101 may exchange setup information over thenegotiation link, exchange timing information, pages or other dataframes, which may include signal condition and device capabilityprofiles, or other setup information (410). Once setup information isexchanged between the network interface circuitry 101 and the network,e.g., an infrastructure node or other network device, the networkinterface circuitry 101 may determine whether the adjustment processingcircuitry 204 or an external command, e.g., from an operator orapplication layer, has indicated a data rate at which to establish thecommunication link (412). If a data rate is specified, then the networkinterface circuitry 101 may request to setup a communication link at therate specified (414). If a data rate is not specified by the adjustmentprocessing circuitry, then the network interface circuitry may select adata rate in accord with the received setup information (416). Forexample, the networking interface circuitry 101 may select the highestdata rate for which the network interface circuitry 101 and the wirelinenetwork are compatible.

If retrain is selected, the network interface circuitry 101 may have anexisting communication link to the wireline network. The networkinterface circuitry 101 may send a retrain indicator to the network(418) over the existing communication link. For example, the retrainindicator may include a particular bit pattern or data frame indicatinga retrain and the data rate for the re-established communication link.Following the retrain indicator, the network interface circuitry 101 mayapply a multiplier to the clock signal for the existing communicationlink (420). The multiplier may increase or decrease the clock signalfrequency by the factor of the multiplier. For example, to double thedata rate of the existing communication link, the network interfacecircuitry 101 may apply a multiplier of 2. Similarly, to halve the datarate, the network interface circuitry 101 may apply a multiplier of 0.5.Thus, the network interface circuitry 101 may apply a multiplier greaterthan one to increase the data rate and a multiplier less than one todecrease the data rate. After the multiplier is applied, the networkinterface circuitry 101 may proceed to send or receive traffic at thenew data rate of the re-established communication link (422).

If establishment/re-establishment fails during retrain orauto-negotiation, the network interface circuitry may reduce the datarate of the communication link being established (424). The networkinterface circuitry 101 may continue to reduce the data rate untilcommunication link establishment is successful. In some cases, aselected threshold number of failures, e.g., consecutive failures, maybe met before the network interface circuitry may reduce the data rateof the communication link being established. For example, the networkinterface circuitry may reduce the data rate of the communication linkbeing established after 3 consecutive failed retrains orauto-negotiations. The network interface circuitry 101 may then proceedwith the establishment/re-establishment at the reduced data rate.

The methods, devices, processing, and circuitry described above may beimplemented in many different ways and in many different combinations ofhardware and software. For example, all or parts of the implementationsmay be circuitry that includes an instruction processor, such as aCentral Processing Unit (CPU), microcontroller, or a microprocessor; anApplication Specific Integrated Circuit (ASIC), Programmable LogicDevice (PLD), or Field Programmable Gate Array (FPGA); or circuitry thatincludes discrete circuitry or other circuit components, includinganalog circuit components, digital circuit components or both; or anycombination thereof. The circuitry may include discrete interconnectedhardware components and/or may be combined on a single integratedcircuit die, distributed among multiple integrated circuit dies, orimplemented in a Multiple Chip Module (MCM) of multiple integratedcircuit dies in a common package, as examples.

The circuitry may further include or access instructions for executionby the circuitry. The instructions may be stored in a tangible storagemedium that is other than a transitory signal, such as a flash memory, aRandom Access Memory (RAM), a Read Only Memory (ROM), an ErasableProgrammable Read Only Memory (EPROM); or on a magnetic or optical disc,such as a Compact Disc Read Only Memory (CDROM), Hard Disk Drive (HDD),or other magnetic or optical disk; or in or on another machine-readablemedium. A product, such as a computer program product, may include astorage medium and instructions stored in or on the medium, and theinstructions when executed by the circuitry in a device may cause thedevice to implement any of the processing described above or illustratedin the drawings.

The implementations may be distributed as circuitry among multiplesystem components, such as among multiple processors and memories,optionally including multiple distributed processing systems.Parameters, databases, and other data structures may be separatelystored and managed, may be incorporated into a single memory ordatabase, may be logically and physically organized in many differentways, and may be implemented in many different ways, including as datastructures such as linked lists, hash tables, arrays, records, objects,or implicit storage mechanisms. Programs may be parts (e.g.,subroutines) of a single program, separate programs, distributed acrossseveral memories and processors, or implemented in many different ways,such as in a library, such as a shared library (e.g., a Dynamic LinkLibrary (DLL)). The DLL, for example, may store instructions thatperform any of the processing described above or illustrated in thedrawings, when executed by the circuitry.

Various implementations have been specifically described. However, manyother implementations are also possible.

What is claimed is:
 1. A device, comprising: network interfacecircuitry; and adjustment processing circuitry configured to: determinea signaling condition, of a wireline medium, based on externalenvironmental conditions surrounding the wireline medium; control,responsive to the signaling condition, the network interface circuitryto establish a communication link over the wireline medium at a firstdata rate with a network device; subsequent to establishing thecommunication link, detect a change in the signaling condition of thewireline medium; control, responsive to the change in the signalingcondition, the network interface circuitry to re-establish thecommunication link at a second data rate different than the first datarate with the network device; determine, based on the signalingcondition and responsive to the network interface circuitry receiving anindicator of a third data rate from the network device, whether thethird data rate is supported by the external environmental conditions;control, in a case that the third data rate is supported by the externalenvironmental conditions, the network interface circuitry to establishthe communication link at the third data rate with the network device;and control, in a case that the third data rate is not supported by theexternal environmental conditions, the network interface circuitry totransmit an error message via the wireline medium to the network device,wherein the second data rate is greater than the first data rate in acase that the change in the signaling condition exceeds an improvementthreshold level, the second data rate is less than the first data ratein a case that the change in the signaling condition is lower than astaggered threshold level that is lower than the improvement thresholdlevel, and the network interface circuitry is configured to: determine asetup protocol for establishing the communication link with the networkdevice; in a case that the network interface circuitry determines thatthe setup protocol is to auto-negotiate, establish a negotiation linkwith the network device, exchange setup information with the networkdevice via the negotiation link, determine whether a data rate isspecified in the setup information, setup the communication link at thespecified data rate in a case that the data rate is specified, and setupthe communication link at a selected data rate in a case that the datarate is not specified; and in a case that the network interfacecircuitry determines that the setup protocol is to retrain, send aretrain indicator to the network device, and apply a multiplier to aclock signal for the first data rate to generate a clock signal for thesecond data rate.
 2. The device of claim 1, wherein the signalingcondition comprises a signal-to-noise ratio for the communication link.3. The device of claim 1, wherein the signaling condition comprises abit-error rate for the communication link.
 4. The device of claim 1,wherein the network interface circuitry is configured to receive aparity coding frame over the communication link.
 5. The device of claim4, wherein the network interface circuitry is configured to receiveparity coding frames periodically while the communication link isactive.
 6. The device of claim 4, wherein the adjustment processingcircuitry is configured to determine the signaling condition byanalyzing the parity coding frame received by the network interfacecircuitry.
 7. The device of claim 1, wherein the adjustment processingcircuitry is configured to: responsive to establishing the communicationlink at the first data rate, start a back-off timer; and forgocontrolling the network interface circuitry to re-establish thecommunication link responsive to a detection of another improvement inthe signaling condition at a first time before an expiration of theback-off timer.
 8. The device of claim 1, wherein the indicator isreceived via the communication link.
 9. A method by a device thatincludes adjustment processing circuitry and network processingcircuitry, the method comprising: by the adjustment processingcircuitry: determining a signaling condition, of a wireline medium,based on external environmental conditions surrounding the wirelinemedium; controlling, responsive to the signaling condition, the networkinterface circuitry to establish a communication link over the wirelinemedium at a first data rate with a network device; subsequent toestablishing the communication link, detecting a change in the signalingcondition of the wireline medium; controlling, responsive to the changein the signaling condition, the network interface circuitry tore-establish the communication link at a second data rate different thanthe first data rate with the network device; determining, based on thesignaling condition and responsive to the network interface circuitryreceiving an indicator of a third data rate from the network device,whether the third data rate is supported by the external environmentalconditions; controlling, in a case that the third data rate is supportedby the external environmental conditions, the network interfacecircuitry to establish the communication link at the third data ratewith the network device; and controlling, in a case that the third datarate is not supported by the external environmental conditions, thenetwork interface circuitry to transmit an error message via thewireline medium to the network device, wherein the second data rate isgreater than the first data rate in a case that the change in thesignaling condition exceeds an improvement threshold level, the seconddata rate is less than the first data rate in a case that the change inthe signaling condition is lower than a staggered threshold level thatis lower than the improvement threshold level, and by the networkinterface circuitry: determining a setup protocol for establishing thecommunication link with the network device; in a case that the networkinterface circuitry determines that the setup protocol is toauto-negotiate, establishing a negotiation link with the network device,exchanging setup information with the network device via the negotiationlink, determining whether a data rate is specified in the setupinformation, setting up the communication link at the specified datarate in a case that the data rate is specified, and setting up thecommunication link at a selected data rate in a case that the data rateis not specified; and in a case that the network interface circuitrydetermines that the setup protocol is to retrain, sending a retrainindicator to the network device, and applying a multiplier to a clocksignal for the first data rate to generate a clock signal for the seconddata rate.
 10. A device, comprising: network interface circuitryconfigured to: determine a setup protocol for establishing acommunication link with a network device over a wireline medium; in acase that the network interface circuitry determines that the setupprotocol is to auto-negotiate, establish a negotiation link with thenetwork device, exchange setup information with the network device viathe negotiation link, determine whether a data rate is specified in thesetup information, setup the communication link at the data rate in acase that the data rate is specified, and setup the communication linkat a selected data rate in a case that the data rate is not specified;and in a case that the network interface circuitry determines that thesetup protocol is to retrain, send a retrain indicator to the networkdevice, and apply a multiplier to a clock signal for the data rate ofthe communication link to re-establish the communication link at a newdata rate; and adjustment processing circuitry configured to: subsequentto the network interface circuitry establishing the communication link,detect a change in a signaling condition of the wireline medium;control, responsive to the change in the signaling condition, thenetwork interface circuitry to re-establish the communication link at afirst data rate different than the data rate with the network device;determine, based on the signaling condition and responsive to thenetwork interface circuitry receiving an indicator of a second data ratefrom the network device, whether the second data rate is supported byexternal environmental conditions of the wireline medium; control, in acase that the second data rate is supported by the externalenvironmental conditions, the network interface circuitry to establishthe communication link at the second data rate with the network device;and control, in a case that the second data rate is not supported by theexternal environmental conditions, the network interface circuitry totransmit an error message via the wireline medium to the network device,wherein the first data rate is greater than the data rate in a case thatthe change in the signaling condition exceeds an improvement thresholdlevel, the first data rate is less than the data rate in a case that thechange in the signaling condition is lower than a staggered thresholdlevel that is lower than the improvement threshold level.